This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Fundamentally, angiogenesis plays a key role in the growth and development of new tissues. In the case of a tumor, however, angiogenesis becomes the primary facilitator of rapid tumor growth and metastasis. As a result, angiogenesis inhibition has become an area of increased focus for researchers and pharmaceutical companies seeking to develop new methods of cancer treatment. Traditionally, the gold-standard technique to quantify tumor vasculature has been the histological estimate of microvascular density (MVD). This method, however, is inherently invasive, time consuming, and suffers from sampling bias. To overcome these limitations, researchers turned to MR tumor vasculature imaging. Some of the most successful reported techniques such as Dynamic Contrast Enhanced (DCE) MRI employ exogenous contrast agents. Methods based on the endogenous contrast, such as Arterial Spin Labeling (ASL) and Blood Oxygen Level Dependent (BOLD) MRI induced by carbogen/hyperoxic challenges were also investigated. These methods, however, do not provide sufficient sensitivity for high-resolution imaging of tumor vasculature. In this study, we carefully induced hypoxia challenge (8% oxygen inhalation) to generate sufficient BOLD contrast (~40%), with which high-resolution tumor vasculature maps were able to be obtained. 3D high-resolution tumor vasculature maps can be acquired in minutes. This technique may provide an efficient research tool for us to quantify tumor size, measure tumor vasculature density, provide early detection of tumor metastasis, monitor the effectiveness of cancer treatment drugs, and could potentially characterize tumor grade and aggressiveness.